Y-shaped RNA structures help?

dear netters,
We require help in finding 2-dimensional evidence of y-shaped introns in
RNA splicing reactions. Is there any particular reference where Y-shaped
molecules were shown in a 2-dimensional gel, similar to the eariler proofs
done with the lariat and extended lariat?
Would you please send answers directly to my email address. I will
summarize responses if required.
thanks
Horst Ibelgaufts